脊髓GRK2/Epac1调控小胶质细胞表型转化在电针缓解慢性痛中的作用研究

Our previous work shown that acupuncture effectively relieves inflammatory, neuropathic pain and cutaneous cancer pain at early stage but has no effect on cancer pain at late stage. Acupuncture exerts its analgesic effects through regulating spinal microglial activation and the proinflammatory cytokines expression. Researches had shown distinct mechanisms contribute to inflammatory, neuropathic pain and cancer pain. Recent reports shown that in chronic pain, decreased spinal G coupled receptor kinase GRK2 was observed. The low GRK2 subsequently facilitates the inhibiting effect of Epac1 on the regulatory element upstream of miR-124 gene, then activates proinflammatory (M1) microglia and deactivate antiinflammatory (M2) microglia. The decreased ratio of GRK2/Epac1 is a key neurobilogical mechanism underlying transition to chronic pain. However, whether GRK2/Epac1 and miR-124 are involved in acupuncture analgesia has not been reported. Our preliminary data showed i.t. injection of GRK2 antisense completely reverses acupuncture analgesia on pain. Hence, the present study is designed to observe the role of GRK2/Epac1 - miR-124 - M1/M2 microglia pathway in acupuncture analgesia on inflammatory, neuropathic pain and cutaneous cancer pain in mice. By comparing the different role of this signal pathway in acupuncture analgesia on different chronic pain, the study will help to further understand the mechanism underlie chronic pain and acupuncture analgesia.

我们以往的工作表明，针刺可以有效缓解炎症痛、神经痛，但只能缓解早期小鼠皮肤癌痛，不能缓解晚期癌痛；针刺可以调节慢性痛时脊髓活化的小胶质细胞，下调致炎因子的表达。研究表明，癌痛与炎症痛、神经痛机理不全相同。慢性痛时，脊髓内G蛋白偶联受体激酶GRK2降低，使得下游Epac1活化，后者直接抑制了miR-124的作用，使得致炎型M1型小胶质细胞活化、抗炎型M2型小胶质细胞受抑制，释放炎症因子增加。脊髓GRK2/Epac1比例决定了慢性疼痛的转归。但是GRK2/Epac1介导的小胶质细胞活化分型以及miR-124在癌痛以及针刺镇痛中的作用至今仍不明确。我们的预实验表明，下调脊髓GRK2水平可以翻转电针的镇痛作用。本项目以小胶质细胞活化分型调节分子GRK2/Epac为切入点，比较脊髓小胶质细胞活化分型在针刺缓解炎症痛、神经痛与皮肤癌痛中的作用差异，来深入理解慢性痛以及针刺镇痛的内在机理。

我们以往的工作表明，针刺对不同的慢性痛的镇痛效果不同；针刺可以调节慢性痛时脊髓活化的小胶质细胞，下调致炎因子的表达。本研究结果显示：1）炎症痛小鼠脊髓背角G蛋白偶联受体激酶GRK2表达降低，皮肤癌痛模型小鼠脊髓背角Epac1表达增高，两者均使得GRK2/Epac1比值降低，产生疼痛；电针通过上调炎症痛脊髓GRK2和下调皮肤癌痛小鼠脊髓Epac1，升高炎症痛或皮肤癌痛小鼠脊髓GRK2/Epac1比值，发挥对炎症痛和早期皮肤癌痛的作用。神经痛时脊髓背角GRK2下调，电针可以上调GRK2表达，并且与炎症痛一致，抑制脊髓GRK2表达也能翻转电针对神经痛的镇痛作用。2）炎症痛时，脊髓内GRK2降低，使得下游Epac1活化，抑制了miR-124的作用，使得致炎型M1型小胶质细胞活化、抗炎型M2型小胶质细胞受抑制，释放致炎因子增加，从而导致疼痛发生；而电针能够通过提高GRK2/Epac1的比例，使得miR-124表达上调，抑制致炎型M1型小胶质细胞的活化，促进抗炎型M2型小胶质细胞的活化，从而缓解炎症痛。3）特异性下调脊髓背角星型胶质细胞内GRK2水平亦能抑制电针对炎症痛的镇痛作用，提示针刺可以通过脊髓星型胶质细胞GRK2来发挥镇痛作用。本项目从脊髓GRK2/Eapc1调控小胶质细胞活化分型的角度研究了针刺镇痛的神经机制，将有助于深入理解慢性痛以及针刺镇痛的内在机理，为针刺镇痛的临床应用提供实验依据。